This invention is directed to novel azo compounds and their use as photogenerating pigments in photoconductive imaging members. More specifically, the present invention is directed to novel 2,7-bis azo pigments and layered photoconductive imaging members comprised of these pigments, and a hole transport layer. In one specific embodiment of the present invention, the layered photoresponsive imaging members are comprised of novel 2,7-bis(1'-azo-2'-hydroxy-3'-naphthanilide)napnthalene and the derivatives thereof, and in contact therewith an aryl amine hole transport layer. The aforementioned imaging members are particularly useful in electrostatographic imaging processes and in printing processes and apparatuses, wherein there is enabled high quality images of excellent resolution, which members because of their low cost are classified as disposable.
Numerous different xerographic photoconductive members are known including, for example, a homogeneous layer of a single material such as vitreous selenium, or a composite layered device containing a dispersion of a photoconductive composition. An example of one type of composite xerographic photoconductive member is described, for example, in U.S. Pat. No. 3,121,006 wherein there is disclosed finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. These members contain, for example coated on a paper backing, a binder layer containing particles of zinc oxide uniformly dispersed therein. The binder materials disclosed in this patent comprise a material such as polycarbonate resins, polyester resins, polyamide resins, and the like, which are incapable of transporting for any significant distance injected charge carriers generated by the photoconductive particles. Accordingly, as a result the photoconductive particles must be in a substantially contiguous particle to particle contact throughout the layer for the purpose of permitting charge dissipation required for a cyclic operation.
There are also known photoreceptor materials comprised of inorganic or organic materials wherein the charge carrier generating, and charge carrier transport functions are accomplished by discrete contiguous layers. Additionally, layered photoreceptor materials are disclosed in the prior art which include an overcoating layer of an electrically insulating polymeric material. However, the art of xerography continues to advance and more stringent demands need to be met by the copying apparatus in order to increase performance standards, and to obtain higher quality images.
Recently, there have been disclosed other layered photoresponsive devices including those comprised of separate generating layers, and transport layers as described in U.S. Pat. No. 4,265,990; and overcoated photoresponsive materials containing a hole injecting layer, overcoated with a hole transport layer, followed by an overcoating of a photogenerating layer, and a top coating of an insulating organic resin, reference U.S. Pat. No. 4,251,612. Examples of photogenerating layers disclosed in these patents include trigonal selenium and phthalocyanines, while examples of transport layers include certain diamines as mentioned herein. The disclosures of each of these patents, namely U.S. Pat. Nos. 4,265,990 and 4,251,612, are totally incorporated herein by reference.
Many other patents are in existence describing photoresponsive devices including layered devices containing generating substances, such as U.S. Pat. No. 3,041,167 which discloses an overcoated imaging member containing a conductive substrate, a photoconductive layer, and an overcoating layer of an electrically insulating polymeric material. This member is utilized in an electrophotographic copying system by, for example, initially charging the member with an electrostatic charge of a first polarity, and imagewise exposing to form an electrostatic latent image which can be subsequently developed to form a visible image.
Furthermore, there are disclosed in U.S. Pat. Nos. 4,232,102 and 4,233,383 photoresponsive imaging members comprised of trigonal selenium doped with sodium carbonate, sodium selenite, and trigonal selenium doped with barium carbonate, and barium selenite or mixtures thereof. Moreover, there are disclosed in U.S. Pat. No. 3,824,099 certain photosensitive hydroxy squaraine compositions. According to the disclosure of this patent, the squaraine compositions are photosensitive in normal electrostatographic imaging systems.
Also known are photoconductive devices containing therein various squaraine compositions. Thus, for example, there are illustrated in U.S. Pat. No. 4,508,803, the disclosure of which is totally incorporated herein by reference, photoconductive devices containing novel benzyl fluorinated squaraine compositions. Specifically, in one embodiment illustrated in the '803 patent there is described an improved photoresponsive device comprised of a supporting substrate, a hole blocking layer, an optional adhesive interface layer, an inorganic photogenerating layer, a photoconducting composition layer comprised of benzyl fluorinated squaraine compositions, and a hole transport layer. Other representative patents disclosing photoconductive devices with squaraine components therein, or processes for the preparation of squaraines include U.S. Pat. Nos. 4,507,408; 4,552,822; 4,559,286; 4,507,480; 4,524,220; 4,524,219; 4,524,218; 4,525,592; 4,559,286; 4,415,639; 4,417,041; and 4,486,520. The disclosures of each of the aforementioned patents are totally incorporated herein by reference.
Also, disclosed in the published literature are composite electrophotographic photosensitive materials with various azo compounds. For example, there are illustrated in Japanese Ricoh Patent Publication No. 6064354, published Apr. 12, 1985, composite photoconductors wherein one of the photoconductor layers contain an azo compound of the formulas as illustrated. Some of the azo photoconductive compounds, of the present invention are related to the aforementioned compounds reference particularly when Z is p--C.sub.6 H.sub.4 --p--C.sub.6 H.sub.4 --p--C.sub.6 H.sub.4, of 1,5-naphthalene. Further, there are illustrated in several U.S. Patents layered organic electrophotographic photoconductor elements with azo, bisazo, or related compounds. Examples of these patents include U.S. Pat. Nos. 4,400,455; 4,551,404; 4,390,608; 4,327,168; 4,299,896; 4,314,015; 4,486,522; 4,486,519; 4,551,404; and Konishiroku Japanese Patent Laid Open Publication No. 60111247.
Although photoconductive imaging members with azo compounds are known, including those that are similar to the azo compounds of the present invention, there remains a need for disposable photoconductor devices. Additionally, there continues to be a need for layered photoresponsive imaging members having incorporated therein certain azo compounds, which members will enable the generation of acceptable high quality images, and wherein these members can be repeatedly used in a number of imaging cycles without deterioration thereof from the machine environment or surrounding conditions. Moreover, there is a need for improved layered photoresponsive imaging members wherein the azo compounds selected for one of the layers are substantially inert to the users of such members. Additionally, there is an important need for layered photoconductors with azo compounds, which photoconductors are of low cost, high sensitivity, and possess high cyclic stability. There also is a need for azo photoconductors that possess high panchromaticity.